Prediction of catalyst bed density and simulation of glycerol steam reformer for hydrogen production

A simple method was proposed to generate a rigid model and to predict the packing density of catalyst using Blender software. It is a free and open-source 3D creation suite animating catalyst pellets freely falling into a container. The effects of different catalyst shapes (sphere and cylinder) and sizes (2–5 mm) on the packing density of catalyst bed were investigated. It was found that the void fraction decreased with decreasing catalyst pellet diameter for all reactor diameters (18-50 mm). Moreover, the void fraction decreased with increasing reactor size for all catalyst shapes and sizes. The results also showed that the void fraction of cylindrical catalyst packing was lower than that of spherical catalyst, likely due to the similar shape between the catalyst pellet and the container. The void fraction of the catalyst bed predicted from Blender was employed in a computational fluid dynamics (CFD) model of glycerol steam reformer for hydrogen production. The reformer was packed with Co-Ni/Al2O3 catalyst and operated at feed temperature of 823 K. Glycerol to steam ratio was at 1:8 in a co-current flow with gas hour space velocity at 43,861 ml hr-1g-1. Small-size catalyst improved mass transfer between external and internal of the catalyst and increased glycerol conversion and hydrogen yield. However, as reducing catalyst size, the void fraction decreased and the pressure drop increased.